Media, in particular flowable media as defined in the present application, are often used in drive technology, for example, as lubricants and/or coolants or as pressure means in hydraulic installations for transmitting energies from a pressure medium source to a consumer. Flowable media, for example, hydraulic oil or other pressurized fluids are in media separating means, such as hydraulic accumulators, which fulfill a wide variety of functions in hydraulic installations and serve, for example, to store energy, to supply a fluid reserve for emergency actuation of power consuming devices, and to provide pressure surge attenuation and the like. Secure and proper operation of a hydraulic installation requires not only knowledge of physical operating parameters such as pressure or flow velocities, but also information about whether the media separating means itself is trouble-free and functions reliably in operation.
DE 101 52 777 A1 describes a device for determining the quality of a medium, in particular a lubricant and/or coolant, having multiple sensors that deliver an electric output signal as a function of the respective sensor-specific input variable. One sensor is a temperature sensor that delivers an output signal basically dependent only on the temperature of the medium and basically independent of the quality of the medium in particular. Another sensor delivers an output signal that depends on the quality of the medium, as well as the temperature of the medium. The sensors used are arranged on a shared substrate, which substrate can be immersed in the respective medium to be tested. The device designed in this way permits determination of quality-determining parameters of flowable media, independently of their prevailing temperature.
DE 10 2009 010 775 A1 describes a media separating means in the form of a hydraulic accumulator for receiving at least a partial volume of a liquid under pressure. The hydraulic accumulator has a housing with at least one connection point for connecting the hydraulic accumulator to a hydraulic device such as a hydraulic circuit. A data memory is a component of the hydraulic accumulator. The data stored in the data memory can be electronically read out by a read and/or write device situated outside of the hydraulic accumulator. The operating state of the hydraulic accumulator can therefore be determined and monitored reliably. The monitoring can also be automated and controlled by a control unit.
With the known approach, an elastomer diaphragm, designed as a bladder, separates two media chambers from one another inside the accumulator housing. One media chamber preferably has a compressible working gas, such as nitrogen gas, as the medium. The other media chamber is fillable with hydraulic fluid as another pressurized medium, coming from the hydraulic device, through the connection point in the accumulator housing. The filling is accomplished against the compressive force of the working gas, such that the elastomeric separating means “contracts” and moves to this extent. If hydraulic fluid is needed again on the part of the hydraulic device, the separating means “relaxes,” and the required amount of fluid is discharged from the accumulator housing through the connection, under the influence of the compressive force of the working gas. A partial amount of fluid usually remains in the accumulator. Due to the permeability of the diaphragm material, an unwanted transfer of the hydraulic fluid to the gas side of the hydraulic accumulator occurs in the long term, which transfer may occur suddenly due to the development of cracks or tears, for example, in the event of failure of the separation diaphragm. The result is that the “working capacity” of the hydraulic accumulator is impaired, or it may even fail completely within the hydraulic circuit, making operation of a hydraulic installation substantially more difficult or even impossible.
DE 40 06 905 A1 has already proposed creating a method and a device that can be used for this method for measuring the pressure of a gas, in particular for determining the gas charge pressure in a hydraulic accumulator and/or for maintaining a preselected pressure setpoint value in the container. An unwanted transfer of hydraulic fluid to the working gas side of the accumulator could be detectable by this system. This approach is relatively complex and is expensive to implement with regard to the multitude of components. Thus, for a corresponding measuring method, a connection that can be used at least temporarily to exchange working gas between the hydraulic accumulator, and a measuring chamber is to be established at least temporarily for a corresponding measuring method. This connection preferably has only a fraction of the container volume and has a pressure measuring apparatus. In addition, the connection between the hydraulic accumulator and a refilling device is also established at least temporarily for maintaining the pressure setpoint value. This refilling device refills the container with gas on the working gas side when the actual pressure value in the container is lower than the setpoint pressure value.